In recent years, compact fluorescent lamps have been downsized in comparable to ordinary incandescent lamps, and invite an increasing replacement demand from such incandescent lamps.
As an example of such a compact fluorescent lamp, Japanese patent application Tokkai 2000-228169 (prior art A) discloses those wherein a fluorescent tube is helically packed.
However, there is a tendency that a heat dissipation efficiency of fluorescent tubes falls down and thus the temperature thereof rises up, along with the downsizing thereof. Such a tendency is especially remarkable in a compact fluorescent lamp in which the fluorescent tube is accommodated in a globe for assimilating its appearance to the ordinary incandescent lamp. When fluorescent-tube encapsulating mercury therein is heated to high temperature, a mercury vapor pressure in the fluorescent tube rises excessively, and its light output falls. Therefore, Japanese Patent 3262168 (prior art B) proposes a technique for optimizing the mercury vapor pressure, raising the mercury vapor pressure at a lighting start, and improving the light flux rise-up characteristic by putting an amalgam mercury and any one of indium, lead, tin, bismuth, etc. in the vicinity of discharge electrode of the fluorescent tube.
On the other hand, Japanese utility patent application Sho 61-63759 (Prior Art C) proposes a technique for inducing a cool spot presenting a desirable temperature capable of holding a high mercury vapor pressure in a low temperature state even in a light-out time to improve the light flux rise-up characteristic by protruding a thin tube from the fluorescent tube, without amalgam. However, Prior art C has a drawback that in case of the fluorescent tube being enclosed in a globe, the temperature of the cool spot fails to fall to a desired temperature, since the heat generated by the So, a cool spot with a desired temperature can be induced on the thin tube by dividing the inside of an envelope containing the globe into a can be divided into a fluorescent tube compartment and a lighting device compartment with a partition, and then protruding the thin tube from the tube end into the lighting device compartment by 5-20 mm long.
In the prior art B provided with a main amalgam and an auxiliary amalgam, mercury transfers from the main amalgam to the auxiliary amalgam lasting for about several weeks or several months until the mercury vapor pressure reaches an equilibrium state after the lamp has lighted out. However, according to an experiment using, for example, an absorption method, the change of the mercury vapor pressure becomes very gradual afterward about 10 hours from the time the light-out. It has been found that in the meantime the mercury vapor pressure is determined by broadly the composition of the main amalgam. (see “2002 Manuscripts of Japan Lighting Society National Conference, No. 7) The mercury vapor released from the auxiliary amalgam near the discharge electrode diffuses toward the center of the fluorescent tube, and spreads entirely in the fluorescent tube within broadly several minutes. The entire of the lamp reaches thermal equilibrium within broadly several tenths of minutes to one hour. At that time, the mercury vapor pressure becomes constant at a vapor pressure determined by the temperature of the main amalgam. At that time, the auxiliary amalgam is 100 degrees C. or more, or in some situations, 200 degrees C. or more. As a result, most mercury is substantially released from the auxiliary amalgam (to be exact, metal substance such as indium constituting the auxiliary amalgam).
However, even a fluorescent lamp equipped with auxiliary amalgam is difficult to raise promptly the mercury vapor pressure just after a lighting start, and to assure a desired lightness.
In a globe-less compact fluorescent lamp, even if a cool spot is inducing on a portion of the fluorescent tube, there is a case that the cool spot fails to become a sufficient low temperature depending to its posture. Merely by dividing the inside of the envelope with a partition and protruding a thin tube into a lighting device compartment by slightly around 5-20 mm, the fluorescent tube compartment is left at a high temperature. So that the protruding portion fails to be sufficiently cooled. In a state that the mercury vapor pressure is relatively high during a light-out state, major part of mercury vapor in the fluorescent tube is converging on the cool spot. Therefore, it takes a long time until the lamp gets warm to the temperature for releasing the mercury vapor from the cool spot by which mercury vapor is emitted from a cool spot at a re-lighting.
The present invention has an object to provide a compact fluorescent lamp having a favorable light flux rise-up characteristic and luminaire using the same, in consideration of resolving the problems as described above.